Permanent magnets have been known since 600 B.C. Since that time scientists and engineers have made various improvements. Many of these improvements are documented in Moskowitz "Permanent Magnet Design and Application Handbook" (Cahners Books International, Inc. 1976) at pages 4-7 which is incorporate herein by reference.
Modern developments in improving magnets have focused for some time on rare earth-transition (RE-TM) magnets. Such magnets have considerably stronger magnetic properties and are approximately 10 times stronger than iron magnets and five times stronger than ferrite magnets.
RE-TM magnets are made from rare earth-transition metal compounds. An accepted definition for such compounds is found in Jandeska, Jr. et al, U.S. Pat. No. 4,325,757 which states, "the chemical combination of a transition metal such as cobalt, nickel, iron, manganese and chrome and a rare earth element such as yttrium, lanthanium, cerium, praseodymium, neodymium, promethium, europium, gadolinium, terbium, dysoprosium, holmium, erbium, thulium, ytterbium, or samarium. The rare earth constituent may also be in the form of mischmetal, naturally occuring or refined combinations of rare earth elements . . . . The rare earth-transition metals suitable for use herein are those having high energy products. The energy product is a measure of the energy that a magnet material can supply to an external magnetic circuit such as a flux field for a D.C. motor, without demagnetizing."
While such RE-TM magnets have extremely desirable magnetic properties, they are difficult to form into shapes useful for a magnet. Consequently, they are extremely expensive. For instance, RE-TM magnetic materials are typically, 80 to 100 times the cost of Alnico magnets and 175-200 times the cost of ferrite magnets. However, the tremendous disparity in the cost has retarded the usage of RE-TM magnets in general commerce.
Recently, efforts have been made to use RE-TM powders in unconventional ways in order to utilize their superior magnetic properties while minimizing the cost. For example, U.S. Pat. No. 4,042,341 and 3,892,601 to Smeggil and Smeggil et al, respectively, which are both incorporated herein by reference have disclosed a method for deposition of substantially uniform layers of transition metal and rare earth metal at temperatures below 1000.degree. C. for the desired thickness. The magnetic film deposited is composed of a plurality of RE-TM compounds depending on the properties desired. The metals are decomposed at 1000.degree. C. to yield vapors, which are then condensed on a substrate to form a continuous, substantially uniform coating or layer of metal thereon.
Additionally, U.S. Pat. No. 4,325,757 supra, which is incorporated herein by reference, discloses a method for forming RE-TM powders directly into radially aligned thin, curved, permanent magnets, particularly for use as magnetic pole pieces. The magnets are preferably thin, self-supporting structures.
Despite the well-funded efforts of some very large and powerful companies as shown by the above disclosures, the processes described above are not likely to bring the RE-TM magnets into common commercial usage. Deposition equipment is expensive and requires very skilled operators. The method described for forming RE-TM powders in U.S. Pat. No. 4,325,757 supra is a complicated and labor intensive process, and is believed to be quite expensive.
The invention disclosed takes a novel approach to the problem of the difficult to work with and expensive high performance magnetic materials. Though simple in nature, the invention reflects a deep and well-reasoned understanding of magnetic materials.